1. Field of the Invention
The present invention pertains to computerized three dimensional geometric modeling systems, and particularly to a three dimensional geometric modeling system which employs multiple concurrent geometric engine types.
2. Related Art and Other Considerations
The computer has greatly affected essentially all forms of information management, including the geometric modeling arts. Nowadays there are numerous computer program products that allow the user to create, store, and modify geometric models and their graphical renderings of various types on a display screen, and to print or otherwise output such geometric models and their renderings. Such geometric models and their graphical renderings span the gambit from simple to complex, and can vary in subject matter, e.g., artistic, industrial, etc. Some geometric modeling computer program products are two dimensional, providing only length and width dimensions of objects. The more complex three dimensional computer program products, on the other hand, provide three dimensionsxe2x80x94length, width, and depth/thickness.
Three dimensional geometric modeling programs can generate a scene or part which can comprise one or more constituent 3D shapes. For example, a scene featuring a simple table would comprise a shape for each leg of the table, as well as a shape for a flat table top. The geometric modeling computer program typically has an executable object used to define and generate each shape. The object for each shape can have several components, the components being a combination of executable code and data structure. For example, a boundary representation (xe2x80x9cB-repxe2x80x9d) component includes a data structure describing the geometry and topology data for the shape (e.g., length, width, depth, and coordinates of the part).
Most three dimensional geometric modeling programs employ a feature-based parametric modeling technique. In feature-based parametric modeling, the executable object for each shape has not only a boundary representation component, but also a history or creation component which includes a data structure reflecting how a shape has been created. That is, the history/creation component includes data which indicates an order or chronological sequence of steps employed to construct the shape. For a simple block, for example, the history/creation component may indicate that the block began as a simple two dimensional rectangle that was extruded into a third dimension. U.S. patent application Ser. No. 08/635,293, filed Apr. 19, 1996, entitled xe2x80x9cIntelligent Shapes For Authoring Three-Dimensional Modelsxe2x80x9d, incorporated herein by reference, discloses shapes having various other components in addition to boundary representation and historical components such as: a visual component; a physical component; a functional component; and a behavioral component.
Parts can be formed from other parts. In geometric modeling terms, the building of more complicated shapes in hierarchical fashion from simpler shapes (known as xe2x80x9cprimitivesxe2x80x9d) is known as xe2x80x9cconstructed solid geometryxe2x80x9d (xe2x80x9cCSGxe2x80x9d). A geometric engine can combine the simpler shapes using various operations (e.g., Boolean operations such as xe2x80x9cintersectxe2x80x9d, xe2x80x9cunitexe2x80x9d, xe2x80x9csubtractxe2x80x9d, etc.). The computer stores the overall (complex) shape as a tree, each of the xe2x80x9cleavesxe2x80x9d of the tree comprising a primitive shape. Typically, when the user wants to modify a feature-based shape by changing any aspect of the shape, the feature-based parametric modeling technique re-evaluates the shape, e.g., goes through the entire CGS history tree in order to revise the part in accordance with the change.
Most three dimensional modeling systems utilize a geometric engine for the purpose of performing various operations and computations for shapes. These operations and computations can take various forms, including (for example) Boolean operations, and typically involve the geometric engine modifying the boundary representation components of one or more shapes involved in the operation. Typically a three dimensional modeling system has one geometric engine for performing all the geometric computations and operations required by the three dimensional modeling system. Geometric data created by the three dimensional modeling system is, therefore, stored in a form (e.g., a file or data stream in a file) which is native to the particular geometric engine creating it.
Often geometric data which is generated at a first three dimensional modeling system must be transferred to a second three dimensional modeling system for copying and/or further developmental work. If it turns out that the second three dimensional modeling system does not have the same geometric engine type as the first three dimensional modeling system which created the geometric data, the data must first be processed by a translator. The translator can be either a stand-alone or separate piece of software unconnected to the three dimensional modeling systems, or integrated in a three dimensional modeling systems. Upon completion of the translation to a form compatible with the geometric engine type of the second three dimensional modeling system, the data can be utilized by the second three dimensional modeling system.
Utilization of the translator as described above is not always successful. In some instances, accurate and complete translations cannot be made. In addition to such fidelity problems, of course, the additional step of employing a translator complicates and slows the entire process.
A few three dimensional modeling systems are able to interchange geometric engine types, i.e., switch between geometric engine types. However, such interchange or switch capability is limited so that only one geometric engine type can be utilized at any given instance. To use another geometric engine type, a reconfiguration of the three dimensional modeling system must occur, with a second geometric engine type then being substituted so that a new three dimensional modeling system results. To replace the geometric engines of these three dimensional modeling systems by different geometric engines is a major effort, if not impossible in some situations. Replacement requires many man years of development work to switch the underlying geometric engine. Therefore, almost all three dimensional modeling systems support only one geometric engine. In such limited situations in which a three dimensional modeling system replaces its original engine type with another engine type, the original engine type is not supported any longer.
What is needed, and an object of the present invention, is a three dimensional computer aided geometric modeling system which provides concurrent utilization of multiple geometric engine types.
A computer program product and system executing/implementing the same provides a visual depiction of a three dimensional object upon a display device. Upon execution, the program establishes for the system (1) a design flow system comprising an object for each of one or more shapes, and (2) a modeling kernel. The design flow system and modeling kernel communicate across COM interfaces. The modeling kernel comprises multiple concurrently available geometric engine types. The modeling kernel comprises multiple geometric engine-specific kernels, with each geometric engine-specific kernel comprising one of the geometric engine types and an associated driver.
Differing shapes or parts in a design or assembly can be associated with respective differing geometric engine types, and can be operated upon by the respective geometric engines in the same assembly. When performing modeling operations, the differing geometric engines types associated with the differing shapes/parts are seamless to users of the three dimensional modeling system, and are conducted from the user""s vantage point as if all shapes/parts are associated with the same geometric engine.
The design flow system of the program also facilitates selection of which of the multiple geometric engine types should at least initially attempt to perform an operation with respect to the one or more shapes. When necessary in preparation for calling the selected geometric engine type, the design flow system obtains a translation of a file of a B-rep body for a shape involved in the operation, the translation making the file of the B-rep body compatible with the geometric engine type selected for the operation. If the first geometric engine type selected by the design flow system is unable to perform the requested operation successfully, the driver of the initially-designated geometric engine type invokes a second geometric engine type for a further attempt or transfer of the operation performance (the invocation being made via the driver for the second geometric engine type). For this transfer, the modeling kernel comprises a cross-kernel communication module through which plural drivers of the kernel communicate for the purpose of transferring performance of the operation. The modeling kernel comprises a translator which, in turn, is invoked by the cross-kernel communication module in conjunction with the transfer of an operation request between geometric engine-specific kernels.